Bug 1204028: Evaluate LHS reference before RHS in destructuring

Issue #73
[Depends on] Bug 1147371: Implement IteratorClose

5 files changed, 51 insertions, 1 deletions

diff --git a/js/src/jit/BaselineCompiler.cpp b/js/src/jit/BaselineCompiler.cpp
index 4dcc10b61..2f0d41707 100644
--- a/js/src/jit/BaselineCompiler.cpp
+++ b/js/src/jit/BaselineCompiler.cpp
@@ -1147,7 +1147,7 @@ BaselineCompiler::emit_JSOP_PICK()
     //     after : A B D E C
 
     // First, move value at -(amount + 1) into R0.
-    int depth = -(GET_INT8(pc) + 1);
+    int32_t depth = -(GET_INT8(pc) + 1);
     masm.loadValue(frame.addressOfStackValue(frame.peek(depth)), R0);
 
     // Move the other values down.
@@ -1166,6 +1166,34 @@ BaselineCompiler::emit_JSOP_PICK()
 }
 
 bool
+BaselineCompiler::emit_JSOP_UNPICK()
+{
+    frame.syncStack(0);
+
+    // Pick takes the top of the stack value and moves it under the nth value.
+    // For instance, unpick 2:
+    //     before: A B C D E
+    //     after : A B E C D
+
+    // First, move value at -1 into R0.
+    masm.loadValue(frame.addressOfStackValue(frame.peek(-1)), R0);
+
+    // Move the other values up.
+    int32_t depth = -(GET_INT8(pc) + 1);
+    for (int32_t i = -1; i > depth; i--) {
+        Address source = frame.addressOfStackValue(frame.peek(i - 1));
+        Address dest = frame.addressOfStackValue(frame.peek(i));
+        masm.loadValue(source, R1);
+        masm.storeValue(R1, dest);
+    }
+
+    // Store R0 under the nth value.
+    Address dest = frame.addressOfStackValue(frame.peek(depth));
+    masm.storeValue(R0, dest);
+    return true;
+}
+
+bool
 BaselineCompiler::emit_JSOP_GOTO()
 {
     frame.syncStack(0);
diff --git a/js/src/jit/BaselineCompiler.h b/js/src/jit/BaselineCompiler.h
index 77f4dd005..60dac0966 100644
--- a/js/src/jit/BaselineCompiler.h
+++ b/js/src/jit/BaselineCompiler.h
@@ -42,6 +42,7 @@ namespace jit {
     _(JSOP_DUP2)               \
     _(JSOP_SWAP)               \
     _(JSOP_PICK)               \
+    _(JSOP_UNPICK)             \
     _(JSOP_GOTO)               \
     _(JSOP_IFEQ)               \
     _(JSOP_IFNE)               \
diff --git a/js/src/jit/IonBuilder.cpp b/js/src/jit/IonBuilder.cpp
index 2e7784ff4..c4df415a4 100644
--- a/js/src/jit/IonBuilder.cpp
+++ b/js/src/jit/IonBuilder.cpp
@@ -1563,6 +1563,7 @@ IonBuilder::traverseBytecode()
               case JSOP_DUP:
               case JSOP_DUP2:
               case JSOP_PICK:
+              case JSOP_UNPICK:
               case JSOP_SWAP:
               case JSOP_SETARG:
               case JSOP_SETLOCAL:
@@ -2017,6 +2018,10 @@ IonBuilder::inspectOpcode(JSOp op)
         current->pick(-GET_INT8(pc));
         return true;
 
+      case JSOP_UNPICK:
+        current->unpick(-GET_INT8(pc));
+        return true;
+
       case JSOP_GETALIASEDVAR:
         return jsop_getaliasedvar(EnvironmentCoordinate(pc));
 
diff --git a/js/src/jit/MIRGraph.cpp b/js/src/jit/MIRGraph.cpp
index 3a363a5bf..d6e0fa8ff 100644
--- a/js/src/jit/MIRGraph.cpp
+++ b/js/src/jit/MIRGraph.cpp
@@ -790,6 +790,19 @@ MBasicBlock::pick(int32_t depth)
 }
 
 void
+MBasicBlock::unpick(int32_t depth)
+{
+    // unpick take the top of the stack element and move it under the depth-th
+    // element;
+    // unpick(-2):
+    //   A B C D E
+    //   A B C E D [ swapAt(-1) ]
+    //   A B E C D [ swapAt(-2) ]
+    for (int32_t n = -1; n >= depth; n--)
+        swapAt(n);
+}
+
+void
 MBasicBlock::swapAt(int32_t depth)
 {
     uint32_t lhsDepth = stackPosition_ + depth - 1;
diff --git a/js/src/jit/MIRGraph.h b/js/src/jit/MIRGraph.h
index b986218f4..705d70fa1 100644
--- a/js/src/jit/MIRGraph.h
+++ b/js/src/jit/MIRGraph.h
@@ -142,6 +142,9 @@ class MBasicBlock : public TempObject, public InlineListNode<MBasicBlock>
     // Move the definition to the top of the stack.
     void pick(int32_t depth);
 
+    // Move the top of the stack definition under the depth-th stack value.
+    void unpick(int32_t depth);
+
     // Exchange 2 stack slots at the defined depth
     void swapAt(int32_t depth);